
Water Pressure Sensor Saunier Duval Themafast F 25 E H MOD Ref. S57205
The water pressure sensor measures the pressure of the circuit and sends the reading to the PCB of the Saunier Duval Themafast F 25 E H MOD boiler. When it fails, it can cause incorrect readings and lockouts due to false low pressure, which may manifest through the fault codes F9, F.73, F.74, or F.75. This component is compatible with various models, including those from the Isofast, Isomax, Isotwin, Themaplus, Themafast, and Themacondens ranges, among others. It should be replaced when pressure issues are detected or when the mentioned codes appear.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference S57205
Pressure sensor with reference S57205. 41 verified compatibilities: C24EV and C28E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval C24EV | Isofast | Contrasted |
| Saunier Duval C28E | Isofast | Contrasted |
| Saunier Duval C28E1 | Isofast | Contrasted |
| Saunier Duval C35E | Isofast | Contrasted |
| Saunier Duval C35E1 | Isofast | Contrasted |
| Saunier Duval F24E | Isofast | Contrasted |
| Saunier Duval F28E | Isofast | Contrasted |
| Saunier Duval F28E1 | Isofast | Contrasted |
| Saunier Duval F35E | Isofast | Contrasted |
| Saunier Duval F35E1 | Isofast | Contrasted |
| Saunier Duval C28E | Isomax | Contrasted |
| Saunier Duval C28E2 | Isomax | Contrasted |
| Saunier Duval F28E | Isomax | Contrasted |
| Saunier Duval F28E2 | Isomax | Contrasted |
| Saunier Duval Condens F35E | Isomax | Contrasted |
| Saunier Duval C24E | Isotwin | Contrasted |
| Saunier Duval F24E | Isotwin | Contrasted |
| Saunier Duval F28E | Isotwin | Contrasted |
| Saunier Duval Condens F30-A | Isotwin | Contrasted |
| Saunier Duval C24E | Themaplus | Contrasted |
| Saunier Duval F24E | Themaplus | Contrasted |
| Saunier Duval F25E | Themaplus | Contrasted |
| Saunier Duval F30E | Themaplus | Contrasted |
| Saunier Duval C24E | Themafast | Contrasted |
| Saunier Duval F24E | Themafast | Contrasted |
| Saunier Duval Condens F24E | Themafast | Contrasted |
| Saunier Duval Condens F30E | Themafast | Contrasted |
| Saunier Duval F24E | Themaclassic | Contrasted |
| Saunier Duval F25E | Themaclassic | Contrasted |
| Saunier Duval C24E | Themaclassic | Contrasted |
| Saunier Duval FAS24E | Themaclassic | Contrasted |
| Saunier Duval FAS25E | Themaclassic | Contrasted |
| Saunier Duval F24E | Themacondens | Contrasted |
| Saunier Duval F25 | Themacondens | Contrasted |
| Saunier Duval FAS25 | Themacondens | Contrasted |
| Saunier Duval C18E | Thematek | Contrasted |
| Saunier Duval C24E | Thematek | Contrasted |
| Saunier Duval F24E | Thematek | Contrasted |
| Saunier Duval C24E | Thema | Contrasted |
| Saunier Duval Condens F25 | Thema | Contrasted |
| Saunier Duval Condens F25 | Semia | Contrasted |
Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.
How to check if ref. S57205 is the part for your boiler
What determines it is not the boiler model, but the reference printed on the part you already have installed.
- Find the reference printed on the installed part and check whether it matches the catalogue reference S57205. If it is not visible, do not identify the part from its shape alone.
- Check the full boiler model on its data plate and look for it in the model associations on this page.
- Compare the connections and physical body with the original part before installation.
- If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Symptoms and faults that the pressure switch S57205 resolves.
The pressure sensor measures the water pressure for the electronics. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler intermittently locks out, sometimes it does and sometimes it doesn't, with no clear relation to usage.
Cause: A pressure switch with unstable contact gives readings that sometimes drop below the minimum and cause a lockout.
Note the time and frequency of the blockage; if it does not coincide with actual visible pressure drops on the manometer, the sensor is the first suspect.
- 02
The pressure indicator or icon on the display is flashing or turning on intermittently.
Cause: Indicate that the signal coming from the sensor oscillates around the warning threshold, which is typical of a sensor that is starting to fail.
Check that the fitting or tube connecting the collector to the water circuit is not scaled or partially blocked.
- 03
After filling the circuit, the boiler still does not start, as if it has not detected the added water.
Cause: If the sensor does not update the reading, the PCB continues to see insufficient pressure even though the circuit is already charged.
Check the pressure with the boiler's manometer after filling; if it reads correctly but the fault continues, the sensor is not communicating the change.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F9 | Water pressure sensor fault. | The S57205 sensor does not deliver a valid signal (loose connector, short circuit, or obstructed hydraulic connection) and the PCB does not 'see' pressure; check wiring and pressure reading in diagnostic/menu and verify that the signal changes when pressurizing. |
| F.73 | Water pressure sensor signal out of range (too low). | Interruption/short circuit of the sensor or ground in the cable; check power supply and sensor signal, continuity of the harness, and ensure the sensor port is not blocked. |
| F.74 | Water pressure sensor signal out of range (usually too high). | Short circuit at 5/24 V or internal fault of the sensor; measure the sensor output and check if it remains fixed at high; inspect wiring and clean the orifice, replacing the sensor if it does not recover. |
| F.75 | No increase in pressure detected when the pump starts (pressure sensor and/or pump). | The sensor does not detect the pressure 'spike' due to a faulty sensor or blocked intake (first rule out air/lack of water/pump); check the pressure reading during start-up in service mode and the continuity/power supply of the sensor. |
These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.
Data sheet for Saunier Duval pressure sensor S57205
- Catalogue reference
- S57205
- Brand
- Saunier Duval
- Type of part
- Pressure sensors
- Units in stock
- 4 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Data read on the part and in the manufacturer's documentation
What we have not been able to verify does not appear here.
- Batch number
- 120521 B
- Secondary code on the label
- 0020016532












